1. Field of the Invention
The present invention relates to a resist pattern forming (formation) method utilizing an imprinting method, and also relates to a magnetic recording medium manufacturing method and a magnetic head manufacturing method, both utilizing the method of forming the resist pattern mentioned above.
2. Related Art
In a method of manufacturing a semiconductor element or recording medium, for example, there is known an optical lithography method for forming a fine resist pattern to a resist layer formed on a substrate surface. In the resist pattern forming method utilizing this optical lithography method, a light is irradiated on the resist layer formed on the substrate surface (for example, a layer formed by applying a resist material, in thin film form, such as a resin which is reacted with light to be hardened) to thereby form a concavo-convex pattern, on the resist layer, which is thereafter developed, thus forming the resist pattern.
Furthermore, in recent years, in order to satisfy requirement of high density of the semiconductor element and increasing of recording capacity of the recording medium, there has been developed an electron-beam lithography technology capable of forming a resist pattern of nano-meter size by irradiating an electron beam in place of the light.
In such electron beam lithography technology, however, the resist pattern formation requires much time, which may provide inconvenience for mass-production, and moreover, an electron-beam lithograph device is expensive, leading to cost-up of a product.
Furthermore, in these days, another resist pattern forming method has been proposed as fine resist pattern forming method (as ‘imprinting method’), for example, as disclosed in “Imprint of sub-25 nm vias and trenches in polymers” (Applied Physics Letters), by Stephen Y. Chou, Nov. 20, 1995, Vol. 67, No. 21, Pages 3114–3116, in which a concavo-convex portion including protrusion and recess of nano-meter size formed to a mold is pressed against the substrate surface to thereby transfer the shape of such concavo-convex portion to thereby form the resist pattern of nano-meter size.
This resist pattern forming method includes the following steps or processes, for example, such as shown in FIGS. 12A to 12D.
With reference to these figures, a mold (which may be called ‘stamper’) 21, as shown in FIG. 12B, having inverted patterns having protrusion 22 and recess 23 to be transferred of a concavo-convex shape and a substrate 11 are heated to a temperature more than a transition temperature of glass of a resist material forming the resist layer 12 and, thereafter, such mold 21 is pressed against the resist layer 12 formed on the surface of the substrate 11 as shown in FIG. 12A.
Next, under the state that the mold 21 is pressed against the resist layer 12, it is cooled to a temperature less than the transition temperature of the glass used as the resist material and then separated from the resist layer 12, whereby, as shown in FIG. 12C, the concavo-convex pattern (including protrusion 15 and recess 14) is transferred to the resist layer 12.
Further, in such processes, a resist material, which is not removed to the other portions at the mold pressing time, remains in the recess 14 of the resist pattern formed on the substrate 11, which is called herein later as ‘resist remaining layer’ denoted by reference numeral ‘3’. For this reason, as shown in FIG. 12D, this resist remaining layer 3 is thereafter removed by, for example, an etching treatment, to thereby expose a substrate surface 16 at this recess 14.
Further, although not directly relating to such imprint method, prior art of, for example, Japanese Patent Laid-open (KOKAI) Publication No. 2000-181082 or No. 2003-231608 discloses a patterning technology as ‘semiconductor manufacturing method’ in which a photoresist (or photo-resist) subjected to pattern exposure is treated by isotopic-etching using ozone to thereby carry out a fine patterning more than that performed by the pattern exposure.
In consideration of countermeasure to the requirement for achieving the high density of the semiconductor element and increasing the recording capacity of the recording medium, in order to make the recording density of the recording medium high, at the time of manufacturing a discrete-track-type magnetic recording medium (called hereunder ‘discrete track medium’), which has been attracted as magnetic recording medium for future generation, it is necessary to make small, by some extent, a track pitch of a data recording track formed with the fine pattern of a layer of the magnetic material (i.e., magnetic layer). Accordingly, it is necessary to reduce, by some extent, the width of a groove between the tracks formed from the magnetic layer, and this groove corresponds to a non-magnetic portion for reducing magnetic influence to the adjacent recording tacks at the time of reading the recorded data.
In this time, in a case where the resist pattern 60 formed by the resist pattern forming method of the characters mentioned above is used as a mask, and as shown in FIG. 13, a metal mask layer 61 and a magnetic layer 62 are etched to thereby form the groove, i.e., non-magnetic portion, 63, the width of the groove to be etched is narrowed, as shown with a broken line in FIG. 13, in the direction separating from the resist pattern 60 (i.e., on the lower side in FIG. 13). For this reason, in a case where the width w7 at the protrusion of the resist pattern 60 is too widened without changing the pitch for forming the data recording track 65, there may cause a fear that it may become difficult to form the groove 63 having a depth reaching the substrate 64.
Accordingly, in order to form a resist pattern having a narrow width of the protrusion, i.e., w7 in FIG. 13, it will be necessary to press the resist layer 12 formed on the surface of the substrate 11 so as to transfer the concavo-convex shape including protrusion and recess of a mold 21a having a narrow width of a recess 23a, (i.e., in other words, a wide width of the protrusion 22a) shown in FIG. 14a. 
However, as shown in FIG. 14A, it is more difficult to form the resist pattern having the narrow width of the protrusion by pressing mold 21a, against the resist layer, having the recess 23a having a narrow width than to form the resist pattern having the protrusion having a wide width by pressing the mold having the wide width of a recess 23b shown in FIG. 14B. That is, in the case of using the mold 21a having the narrow recess 23a, it contacts the resist layer 12 at a wide area, which requires a high load to the mold 21a for pressing the resist layer 12, and in addition, the formed resist pattern may be ready peeled at the time of separating the mold 21a from the resist layer 12. Such adverse phenomenon will become remarkable in a case of using a mold having a line-and-space pattern in which recesses and protrusions are periodically arranged as shown in FIGS. 14A and 14B.